# Using braces with equations - how to make fractional terms 'bigger'

I have some equations which display perfectly until I put them inside a brace and they become 'squashed'. Example:

\begin{alignat}{2}
u =  \frac{\partial\tilde{X}}{\partial x},
v =  \frac{\partial\tilde{X}}{\partial y}
\end{alignat}

\begin{alignat}{2}
\left\{
\begin{array}{l}
u =  \frac{\partial\tilde{X}}{\partial x}\\
v =  \frac{\partial\tilde{X}}{\partial y}
\end{array}\right.
\end{alignat}


i.e. the tilde notation cannot be seen clearly in the second equation inside the brace. I have some complex equations which look brutal inside braces is there a way to display these more clearly?

• You use \begin{alignat}{2}, but do not align whatever! – Bernard Jun 30 '16 at 18:44
• Material in an array environment is set in \textstyle math mode by default, even if thearray is embedded in a display math environment. Hence, either use \dfrac inside the array to get "large" fractional expressions, or use another math environment that sets its material in \displaystyle. – Mico Jun 30 '16 at 21:56

## 2 Answers

Consider using a dcases environment (provided by the mathtools package) instead of an array environment for the second equation. Incidentally, since no vertical aligning seems to be performed, consider using basic equation environments instead of alignat environments. In addition, you may want to use \widetilde instead of \tilde for the capital X letters.

\documentclass{article}
\usepackage{mathtools}  % for 'dcases' environment
\begin{document}

$$u = \frac{\partial\widetilde{X}}{\partial x}, \quad v = \frac{\partial\widetilde{X}}{\partial y}$$

$$\begin{dcases} u = \frac{\partial\widetilde{X}}{\partial x}\\[1ex] v = \frac{\partial\widetilde{X}}{\partial y} \end{dcases}$$
\end{document}


\dfrac from amsmath and some vertical correction should be enough:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{alignat}{2}
u =  \frac{\partial\tilde{X}}{\partial x},v =  \frac{\partial    \tilde{X}}{\partial y}
\end{alignat}

\begin{alignat}{2}
\left\{
\begin{array}{l}
u =  \dfrac{\partial\tilde{X}}{\partial x}\\[9pt] %the value up to you
v =  \dfrac{\partial\tilde{X}}{\partial y}
\end{array}\right.
\end{alignat}
\end{document}